This SBIR phase I project proposes a novel all-fiber and ultra compact high power nanosecond fiber laser system by using our proprietary technologies on spectral shaping and pulse shaping. The proposed idea is an enabling technology for portable photoacoustic microscopy. It is a specialty fiber based MOPA. Our unique spectral shaping techniques enable us to reduce the SBS and ASE noise significantly in the amplifier for commercially available YDFs and to reuse the residual pump to further increase the efficiency. These will make the fiber laser system superior in terms of wall plug efficiency (over 20%), power (>10 W and >100 kW peak power), noise, size, and cost. The cost and size will be at least ten times cheaper than other competing approaches. The design is simpler in construction and easy to operate. In Phase I time frame, a prototype 1064 nm fiber laser operating at output energy of 0.5 mJ will be built up and preliminary test will be done for imaging. Fine tuning of the product to achieve more compact size and generation of second harmonic green light laser and several imaging applications (in collaboration with Washington University) will be given in Phase II with an investigation of volume production. PUBLIC HEALTH RELEVANCE: The proposed portable photoacoustic microscopy provides a breakthrough in applying nanosecond fiber laser technology into real clinic. Though photoacoustic microscopy is our first application in obtaining deep tissue high resolution image, it will have significant impact to other biomedical applications.